Which Direct Acting Parasympathomimetic can be used for smoking cessation?

• A. Pilocarpine
• B. Methacholine
• C. Varenicline
• D. Demecarium

Answer: (C)

Partial activation of nicotinic acetylcholine receptors in the brain can help with smoking cessation by easing withdrawal and reducing the rewarding effects of nicotine. Varenicline does exactly this: it is a selective partial agonist at the alpha4beta2 nicotinic receptors. By partially stimulating these receptors, it diminishes cravings and withdrawal, while also blocking nicotine from producing the same dopamine-driven reward if you smoke again. This direct action on nicotinic receptors makes it effective for helping people quit.

The other options act differently: pilocarpine and methacholine are muscarinic agonists, which don’t address nicotine receptor–related addiction. Demecarium is an acetylcholinesterase inhibitor that increases acetylcholine indirectly. These mechanisms aren’t used for smoking cessation.